Internet protocol (IP) multimedia subsystem (IMS) is defined by the Third Generation Partnership Project (3GPP) as a new mobile network infrastructure that enables the convergence of data, speech, and mobile network technology over an IP-based infrastructure. IMS bridges the gap between the existing traditional telecommunications technology and Internet technology, allowing network operators to offer a standardized, reusable platform with new, innovative services by enhancing real time, multimedia mobile services, such as voice services, video telephony, messaging, conferencing, and push services. IMS can be used to provide services for both mobile networks and landline networks at the same time, providing unique mixtures of services with transparency to the end-user.
The main function of IMS is to set up media communication sessions between users and between users and applications. IMS supports the establishment of any type of media session (e.g., voice, video, text, etc.) and provides the service creator the ability to combine services in the same session and dynamically modify sessions “on the fly” (e.g., adding a video component to an existing voice session). As a result, new and innovative user-to-user and multi-user services become available, such as enhanced voice services, video telephony, chat, push-to-talk, and multimedia conferencing, all of which are based on the concept of a multimedia session. The underlying IMS infrastructure enables mobile IP communication services via its ability to find a user in the network and then to establish a session with the user. The key IMS components enabling mobility management are the call session control function (CSCF) and home subscriber server (HSS). The CSCF is essentially a proxy, which aids in the setup and management of sessions and forwards messages between IMS networks. The HSS holds all of the key subscriber information and enables users (or servers) to find and communicate with other end users.
FIG. 1 is a block diagram illustrating a conventional IMS system. In FIG. 1, a visited network 100 includes a proxy CSCF (P-CSCF) 102. The visited network 100 may be part of or in communication with a mobile or fixed network. Accordingly, visited network 100 includes a gateway general packet radio service (GPRS) support node (GGSN) 104, which may in turn communicate with a serving GPRS support node (SGSN) 106 that is in communication with a radio access network (RAN) 108 in which an IMS subscriber is currently located. The subscriber's home network 110 includes an HSS 112 with the subscriber's profile, an interrogating CSCF (I-CSCF) 114, and a serving CSCF (S-CSCF) 116.
IMS uses session initiation protocol (SIP) for multimedia session negotiation and session management. For example, SIP REGISTER and INVITE messages are used for communication between P-CSCF 102, I-CSCF 114, and S-CSCF 116 in FIG. 1. In the example illustrated in FIG. 1, the IMS nodes function collectively as a mobile SIP network, providing routing, network location, and addressing functionalities. The DIAMETER protocol is used between I-CSCF 114 and HSS 112 and between S-CSCF 116 and HSS 112. DIAMETER provides an authentication, authorization and accounting (AAA) framework for applications such as network access or IP mobility in both local and roaming situations.
P-CSCF 102 is the first contact point within the IMS and behaves like a proxy. The P-CSCF 102 forwards a SIP REGISTER request received from the subscriber's user equipment (UE) (not shown) via GGSN 104, SGSN 106, and RAN 108 to I-CSCF 114, whose identity is determined using the home domain name, as provided by the UE. After registration is performed, SIP messages concerning the registered subscriber are forwarded to S-CSCF 116, whose identity P-CSCF 102 received as a result of the registration procedure. P-CSCF 102 also forwards SIP requests or responses to the UE, generates call detail records (CDRs), maintains a security association between itself and each UE, performs SIP message compression and decompression, and authorizes bearer resources and QoS management.
I-CSCF 114 is the contact point within the subscriber's home network 110 for all communication sessions destined for the subscriber or for a roaming subscriber currently located within that network operator's service area. I-CSCF 114 locates and assigns S-CSCF 116 to a user initiating SIP registration, routes a SIP request received from another network to S-CSCF 116, obtains the address of S-CSCF 116 from HSS 112 and forwards the SIP request or response to the S-CSCF 116.
S-CSCF 116 performs the session control services for the UE and maintains session state as needed by the network operator for support of the services. S-CSCF 116 accepts registration requests, obtains IMS subscription information from HSS 112, and provides session control. S-CSCF 116 also acts as a proxy server, i.e., it accepts requests and services them internally or forwards them on, and behaves as a User Agent, i.e., it terminates and independently generates SIP transactions. S-CSCF 116 is responsible for interaction with services platforms for the support of services on behalf of an originating endpoint.
HSS 112 holds the subscriber profile and keeps track of the core network node that is currently holding the subscriber. HSS 112 provides mobility management, call and/or session establishment support, and supports the call and/or session establishment procedures in IMS. HSS 112 supports user security information generation, authentication procedures, user identification handling, access authorization, service authorization support service provisioning support, and provides support for application services. HSS 112 may also communicate with an application server (not shown) to offer value added services. The application server and can reside either in the user's home network or in a third party location and enables different services in the IMS network, such as call-forwarding, call waiting, presence and instant messaging. The application server communicates with the HSS using the DIAMETER protocol.
The P-CSCF, I-CSCF, S-CSCF, and HSS functions are all defined in the 3GPP specifications. However, the 3GPP specifications do not map these components to hardware. Moreover, the 3GPP specifications suggest an implementation, such as that illustrated in FIG. 1, where the components are implemented on separate nodes that communicate with each other over a wide area network. For example, in FIG. 1, the S-CSCF 116 and HSS 112 communicate with each other via the diameter protocol over a wide area network 110.
One problem associated with an implementation, such as that illustrated in FIG. 1 where the IMS functions are implemented on separate nodes that communicate with each other over a wide area network, is that the volume of information exchanged between the functions can place a burden on the communications network and/or increase session setup time. For example, in light of the amount of subscription information that is stored by HSS 112 that must be communicated to S-CSCF 116, the link between S-CSCF 116 and HSS 112 may become a bottleneck. Current 3GPP standards do not address such issues.
Accordingly, in light of these difficulties associated with IMS networks, there exists a need for methods, systems, and computer program products for clustering and communicating between IMS entities.